This invention relates to pitot pumps, and more particularly to a system for self-cooling the lubricant for the bearings of a high-speed pitot pump.
Generally speaking, a pitot pump has a fixed housing and a rotatable casing mounted on the end of a drive shaft supported by high-speed bearings such as roller or ball bearings. A fixed pitot tube is mounted in the casing for withdrawing fluid from near the periphery of the casing as the casing rotates. This results in high pressure fluid being discharged through an outlet from the rotatable casing. The casing typically is secured to an axial shaft driven by a prime mover such as an electric motor. Pitot pumps which operate at speeds of about 3500 rpm typically have grease lubricated bearings for supporting the casing shaft. Such pitot pumps are described and illustrated in U.S. Pat. Nos. 3,384,024 and 3,795,459, for example.
In high-speed pitot pumps operating at about 5000 to 8500 rpm grease lubricated bearings are not satisfactory and lubricating oil is preferred for lubricating the bearings. The lubricating oil becomes relatively hot during continuous high-speed operation of the pump. If the lubricating oil becomes excessively hot, its lubricity can be degraded, resulting in premature bearing failure. Hence, there is a need for a system to prevent excessive heat build-up in the lubricant used for the bearings in such pumps.